The invention relates to improvements in a method and apparatus for producing molten pig iron or steel pre-products and reduction gas in a melt-down gasifier. In a known method, a first fluidized-bed zone is formed by coke particles, with a heavy motion of the particles, above the blow-in plane (first blow-in plane) by the addition of coal and by blowing in oxygen-containing gas. Iron sponge particles and/or pre-reduced iron ore particles are added to the first fluidized bed from above, with a substantial portion of the particle sizes being more than 3 mm are added to the first fluidized-bed zone from above the process is carried out in a melt-down gasifier, which is comprised of a refractorily lined vessel having openings for the addition of coal, ferrous material as well as for the emergence of the reduction gases produced. The lined vessel furthermore has openings for tapping the metal melt and the slag, and has pipes or nozzles which enter into the melt-down gasifier above the slag level at at least two different heights.
A method of this kind is known from European Patent B1-0010627. There, a coal fluidized-bed with a high-temperature zone in the lower region is produced in a melt-down gasifier, to which iron sponge particles are added from above. On account of the impact pressure and buoyancy forces in the coal fluidized-bed, iron sponge particles having sizes greater than 3 mm are considerably braked and substantially elevated in temperature by the heat exchange with the fluidized bed. They impinge on the slag layer forming immediately below the high-temperature zone at a reduced speed and are melted on or in the same. The maximum melting performance of the melt-down gasifier, and thus the amount and temperature of the molten pig iron produced, not only depends on the geometric dimensions of the melt-down gasifier, but also are determined to a large extent by the quality of the coal used and by the portion of larger particles in the iron sponge added. When using low-grade coal, the heat supply to the slag bath, and thus the melting performance for the iron sponge particles, decline accordingly. In particular, with a large portion of iron sponge particles having grain sizes of above 3 mm, which cannot be heated to the same extent as smaller particles by the coal fluidized-bed when braked in their fall and which, therefore, necessitate a higher melting performance in the region of the slag layer, the reduced melting performance has adverse effects in case low-grade coal is used.
By German Pat. No. 1017314 a method for producing burnable gases from dustlike to coarsely grained fuels is known, with which two fluidized-bed zones of coke particles are formed in a gas generator, wherein the upper zone, which is supplied with an endothermally reacting gasifying agent, is maintained in a heavily whirling motion and the lower zone, which is supplied with an exothermally reacting gasifying agent, is maintained in a a state ranging from unnoticeable to weak motion of the coke particles. In this manner, it is possible to reduce considerably the heat transported away through the whirling fuel at the site where the exothermic gasifying agents are supplied and to strip off the gasification residues, which sink down from the upper fuel layers as melted slag. In the "hot zone" of the gas generator, temperatures of 1,500.degree. C. and more may be attained. According to this publication, it is also considered feasible to introduce ores together with the fuels into the gas generator and to tap the melted metal collecting on the bottom of the gas generator below the melted slag in a liquid state. In practice, the utilization of ores has not become notorious in connection with such a method for producing burnable gases. In this way, it is at best possible to reduce and melt fine ores in slight amounts.
By German Pat. No. 1086256 a method for recovering iron from dustlike or fine-grained iron ores has become known, with which a coke solid-bed is formed in a melting vessel by the addition of coke, in whose lower region a combustion medium, such as oxygen-enriched air, is injected immediately above the slag bath level. Above the coke solid-bed dust coal, pre-reduced ore and oxygen-enriched air are introduced into the melting chamber above the coke solid-bed, with molten iron and molten slag forming, falling down in droplets to the major portion and thus impinging on the coke solid-bed. In the latter, the slag is completely reduced, the iron is deoxidized and carburized, desulphurized and, if desired, enriched with predetermined alloying components. The burnable gases forming above the coke solid-bed flow upwardly and take the cold ore dust introduced into the melting chamber through upper entrance openings with them in order to pre-reduce the same in a separate pre-reduction chamber, from which it is then taken to be blown into the melting chamber. Also this method is suited only to recover iron from dustlike or fine-grained iron ores, but not when charging iron sponge particles having a substantial portion of particle sizes of above 3 mm.